Lupus . Lupus affects multiple organs and is a systemic disease. Facial swelling should be analysed in conjuntion with over all clinical picure . It could be due to several reasons based on target organ or system involvement in lupus which include heart , pulmonary atreies, kidneys , small blood vessel inflammation , anemia, skin etc. Fu with a rheumatologist.

Go back to doctor. This may be related to the Prednisone you are taking, but also may be secondary to complications of the sle. Best to be examined and appropriately evaluated than to be wondering. Good luck and best wishes.